//! Live UI for `pkh deb`: a status bar with the current build phase on top
//! and a rolling pane of rewritten log lines below ("a terminal in the
//! terminal").
//!
//! Subprocess output is captured through a [`LineSink`] implementation,
//! rewritten by classifiers ([`crate::ui::logfmt`]) and rendered in place
//! with indicatif, so pkh's own log lines keep printing above the widget via
//! `indicatif-log-bridge`. Every raw captured line is also tee'd to a log
//! file under the pkh cache directory.

use std::collections::VecDeque;
use std::fs::{self, File};
use std::io::Write;
use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant};

use crossterm::{cursor, execute, style::Stylize, terminal::Clear, terminal::ClearType};
use directories::ProjectDirs;
use indicatif::{MultiProgress, ProgressBar, ProgressStyle};

use crate::context::{LineSink, Stream};
use crate::ui::logfmt::{
    Action, AptInstallClassifier, AptUpdateClassifier, Classifier, GenericClassifier,
    MakeClassifier, MmdebstrapClassifier, QuiltClassifier,
};

/// Number of lines displayed in the rolling pane
const PANE_LINES: usize = 4;

/// Minimum interval between pane redraws
const REDRAW_INTERVAL: Duration = Duration::from_millis(50);

/// Build phases of `pkh deb`, shown in the status bar
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Phase {
    /// Downloading the chroot tarball (mmdebstrap)
    PreparingChroot,
    /// Extracting the chroot tarball
    ExtractingChroot,
    /// Device nodes, /proc bind mount, etc.
    FinalizingChroot,
    /// apt-get update
    UpdatingPackageLists,
    /// Installing build-essential & co
    InstallingEssentials,
    /// quilt push -a
    ApplyingPatches,
    /// --inject packages
    InjectingPackages,
    /// apt-get build-dep
    InstallingBuildDeps,
    /// debian/rules build
    Building,
    /// fakeroot debian/rules binary
    ProducingBinaries,
    /// Retrieving produced .deb files
    RetrievingArtifacts,
}

impl Phase {
    /// Human-readable label displayed in the status bar
    pub fn label(&self) -> &'static str {
        match self {
            Phase::PreparingChroot => "Preparing chroot",
            Phase::ExtractingChroot => "Extracting chroot",
            Phase::FinalizingChroot => "Finalizing chroot",
            Phase::UpdatingPackageLists => "Updating package lists",
            Phase::InstallingEssentials => "Installing essential packages",
            Phase::ApplyingPatches => "Applying patches",
            Phase::InjectingPackages => "Injecting packages",
            Phase::InstallingBuildDeps => "Installing build dependencies",
            Phase::Building => "Building package",
            Phase::ProducingBinaries => "Producing binary packages",
            Phase::RetrievingArtifacts => "Retrieving artifacts",
        }
    }
}

/// Default classifier used for a given phase
fn default_classifier(phase: Phase) -> Box<dyn Classifier> {
    match phase {
        Phase::PreparingChroot => Box::new(MmdebstrapClassifier::new()),
        Phase::ExtractingChroot | Phase::FinalizingChroot => Box::new(GenericClassifier::new()),
        Phase::UpdatingPackageLists => Box::new(AptUpdateClassifier::new()),
        Phase::InstallingEssentials => Box::new(AptInstallClassifier::new("Installing essentials")),
        Phase::ApplyingPatches => Box::new(QuiltClassifier::new(0)),
        Phase::InjectingPackages => Box::new(AptInstallClassifier::new("Injecting packages")),
        Phase::InstallingBuildDeps => {
            Box::new(AptInstallClassifier::new("Installing build dependencies"))
        }
        Phase::Building | Phase::ProducingBinaries => Box::new(MakeClassifier::new()),
        Phase::RetrievingArtifacts => Box::new(GenericClassifier::new()),
    }
}

/// Visual kind of a pane line, driving its color
#[derive(Debug, Clone, Copy, PartialEq)]
enum Kind {
    Normal,
    Warning,
    Error,
}

/// Mutable state shared between the sink and the widget
struct Pipeline {
    classifier: Box<dyn Classifier>,
    lines: VecDeque<(Kind, String)>,
    errors: Vec<String>,
    last_draw: Instant,
    bar_total: u64,
}

/// State shared between [`DebUi`] and its sinks
struct Shared {
    top: ProgressBar,
    pane: ProgressBar,
    state: Mutex<Pipeline>,
    tee: Mutex<Option<File>>,
    log_path: Mutex<PathBuf>,
    timestamp: String,
    enabled: bool,
    /// Set once the widget has been removed from the terminal; afterwards all
    /// rendering is skipped so late events cannot redraw stale frames.
    suspended: AtomicBool,
    started: Instant,
}

/// Live build view for `pkh deb`
///
/// Create one per build (disabled automatically when stdout is not a TTY or
/// when the user requests verbose output), pass it down as
/// `Option<Arc<DebUi>>`, and feed subprocess output through [`DebUi::sink`].
pub struct DebUi {
    shared: Arc<Shared>,
}

impl DebUi {
    /// Create a live view attached to `multi`
    ///
    /// When stdout is not a TTY, the widget is disabled: no bars are drawn,
    /// but captured output is still tee'd to the log file.
    pub fn new(multi: &MultiProgress) -> Self {
        let enabled = is_stdout_tty();

        let top = if enabled {
            let pb = multi.add(ProgressBar::new(0));
            pb.enable_steady_tick(Duration::from_millis(80));
            pb.set_style(spinner_style());
            pb.set_prefix("Building package");
            pb.set_message("(starting…)");
            pb
        } else {
            ProgressBar::hidden()
        };

        let pane = if enabled {
            let pb = multi.add(ProgressBar::new(0));
            pb.enable_steady_tick(Duration::from_millis(150));
            // No template margin: multi-line messages are only prefixed by
            // the template on their first line, which would misalign the
            // pane; each rendered line carries its own indent instead.
            pb.set_style(
                ProgressStyle::default_bar()
                    .template("{msg}")
                    .expect("valid template"),
            );
            pb.set_message("  │ (starting…)");
            pb
        } else {
            ProgressBar::hidden()
        };

        let timestamp = chrono::Utc::now().format("%Y%m%dT%H%M%S").to_string();
        let log_path = default_log_path(&timestamp);

        let ui = Self {
            shared: Arc::new(Shared {
                top,
                pane,
                state: Mutex::new(Pipeline {
                    classifier: Box::new(GenericClassifier::new()),
                    lines: VecDeque::new(),
                    errors: Vec::new(),
                    last_draw: Instant::now(),
                    bar_total: 0,
                }),
                tee: Mutex::new(None),
                log_path: Mutex::new(log_path.clone()),
                timestamp,
                enabled,
                suspended: AtomicBool::new(false),
                started: Instant::now(),
            }),
        };

        if ui.shared.enabled {
            install_sigint_hook(&log_path);
        }

        ui
    }

    /// Identify the package being built; names the log file and the status bar
    pub fn set_target(&self, package: &str, version: &str, series: &str, arch: &str) {
        if self.shared.enabled {
            self.shared.top.set_prefix(format!(
                "Building {package} ({version}) for {series}/{arch}"
            ));
        }

        // Rename the log file to include the package identity (best-effort),
        // then open it so subsequent captured lines are tee'd.
        let old_path = self.shared.log_path.lock().unwrap().clone();
        let log_path = match old_path.parent() {
            Some(dir) => dir.join(format!(
                "deb-{package}-{version}-{}.log",
                self.shared.timestamp
            )),
            None => old_path.clone(),
        };
        let _ = fs::rename(&old_path, &log_path);
        *self.shared.log_path.lock().unwrap() = log_path.clone();
        update_sigint_log_path(&log_path);

        if let Some(dir) = log_path.parent() {
            let _ = fs::create_dir_all(dir);
        }
        match File::create(&log_path) {
            Ok(mut file) => {
                let _ = writeln!(
                    file,
                    "# pkh deb {} ({}) for {}/{} started {}",
                    package,
                    version,
                    series,
                    arch,
                    chrono::Utc::now().to_rfc3339()
                );
                *self.shared.tee.lock().unwrap() = Some(file);
            }
            Err(e) => {
                log::warn!(
                    "Could not create build log file {}: {}",
                    log_path.display(),
                    e
                );
            }
        }
    }

    /// Switch to a phase, installing its default classifier
    pub fn phase(&self, phase: Phase) {
        self.phase_with(phase, default_classifier(phase));
    }

    /// Switch to a phase with a custom classifier (e.g. quilt with a known
    /// patch count)
    pub fn phase_with(&self, phase: Phase, classifier: Box<dyn Classifier>) {
        {
            let mut st = self.shared.state.lock().unwrap();
            st.classifier = classifier;
            st.lines.clear();
            st.bar_total = 0;
            st.last_draw = Instant::now();
        }
        if self.shared.enabled {
            self.shared.top.set_style(spinner_style());
            self.shared.top.set_message(phase.label());
            self.shared.pane.set_message("");
        }
    }

    /// Update the status bar message directly (for in-process work such as
    /// tarball extraction that has no subprocess output)
    pub fn progress_message(&self, msg: &str) {
        if self.active() {
            self.shared.top.set_message(msg.to_string());
        }
    }

    /// Drive the determinate progress bar directly (e.g. artifact retrieval)
    pub fn count_progress(&self, label: &str, pos: usize, total: usize) {
        if !self.active() || total == 0 {
            return;
        }
        apply_progress(
            &self.shared.top,
            &mut self.shared.state.lock().unwrap(),
            pos as u64,
            total as u64,
        );
        self.shared.top.set_message(label.to_string());
    }

    /// Whether the widget is enabled and still drawn
    fn active(&self) -> bool {
        self.shared.enabled && !self.shared.suspended.load(Ordering::SeqCst)
    }

    /// Obtain a sink feeding this view; pass it to `ContextCommand::capture`
    pub fn sink(self: &Arc<Self>) -> Arc<dyn LineSink> {
        Arc::new(Sink {
            shared: self.shared.clone(),
        })
    }

    /// Remove the widget from the terminal (e.g. before printing passthrough
    /// diagnostics or letting child cleanup commands write to the terminal);
    /// idempotent
    ///
    /// Steady ticks are disabled first: otherwise a tick can redraw a frame
    /// right after the clear, leaving stale copies of the widget on screen.
    pub fn suspend(&self) {
        if !self.shared.enabled {
            return;
        }
        if self.shared.suspended.swap(true, Ordering::SeqCst) {
            return;
        }
        self.shared.top.disable_steady_tick();
        self.shared.pane.disable_steady_tick();
        self.shared.top.finish_and_clear();
        self.shared.pane.finish_and_clear();
    }

    /// Clear the widget and print a success summary with the artifacts
    pub fn finish_success(&self, artifacts: &[PathBuf], elapsed: Duration) {
        self.suspend();
        if self.shared.enabled && !artifacts.is_empty() {
            for artifact in artifacts {
                println!("  → {}", artifact.display());
            }
            println!("  ✔ Built in {}s", elapsed.as_secs());
        }
    }

    /// Clear the widget and print a failure summary (recent captured errors
    /// and the path to the full log)
    pub fn finish_failure(&self) {
        self.suspend();

        let st = self.shared.state.lock().unwrap();
        if self.shared.enabled && !st.errors.is_empty() {
            eprintln!("Last captured errors:");
            for err in st
                .errors
                .iter()
                .rev()
                .take(5)
                .collect::<Vec<_>>()
                .iter()
                .rev()
            {
                eprintln!("  {}", err);
            }
        }
        let log_path = self.shared.log_path.lock().unwrap().clone();
        if log_path.exists() {
            eprintln!("Full log: {}", log_path.display());
        }
    }

    /// Time elapsed since the view was created
    pub fn elapsed(&self) -> Duration {
        self.shared.started.elapsed()
    }

    /// Path of the full build log file
    pub fn log_path(&self) -> PathBuf {
        self.shared.log_path.lock().unwrap().clone()
    }
}

impl Drop for DebUi {
    fn drop(&mut self) {
        // Safety net: clear the widget on early returns/unwinds
        self.suspend();
    }
}

/// Bridge forwarding captured subprocess lines into the pipeline
struct Sink {
    shared: Arc<Shared>,
}

impl LineSink for Sink {
    fn line(&self, stream: Stream, line: &str) {
        // Tee the raw line first: nothing should be lost, even when the
        // widget is disabled.
        {
            let mut tee = self.shared.tee.lock().unwrap();
            if let Some(file) = tee.as_mut() {
                let _ = writeln!(file, "{line}");
            }
        }

        if !self.shared.enabled || self.shared.suspended.load(Ordering::SeqCst) {
            return;
        }

        let mut st = self.shared.state.lock().unwrap();
        for action in st.classifier.feed(stream, line) {
            match action {
                Action::Hidden => {}
                Action::Progress { pos, total } => {
                    apply_progress(&self.shared.top, &mut st, pos, total)
                }
                Action::Shown(text) => push_line(&self.shared, &mut st, Kind::Normal, text),
                Action::Warning(text) => push_line(&self.shared, &mut st, Kind::Warning, text),
                Action::Error(text) => {
                    if st.errors.len() < 100 {
                        st.errors.push(text.clone());
                    }
                    push_line(&self.shared, &mut st, Kind::Error, text);
                }
            }
        }
    }
}

/// Update the determinate progress bar, restyling it when needed
fn apply_progress(top: &ProgressBar, st: &mut Pipeline, pos: u64, total: u64) {
    if total == 0 {
        return;
    }
    if st.bar_total != total {
        st.bar_total = total;
        top.set_style(determinate_style());
        top.set_length(total);
    }
    top.set_position(pos.min(total));
}

/// Push a line into the rolling pane and redraw (throttled)
///
/// When the pane is full, the oldest non-error line is dropped first so
/// errors stay visible longer.
fn push_line(shared: &Shared, st: &mut Pipeline, kind: Kind, text: String) {
    st.lines.push_back((kind, text));
    while st.lines.len() > PANE_LINES {
        let drop_idx = st
            .lines
            .iter()
            .position(|(k, _)| *k != Kind::Error)
            .unwrap_or(0);
        st.lines.remove(drop_idx);
    }

    let now = Instant::now();
    if now.duration_since(st.last_draw) >= REDRAW_INTERVAL {
        st.last_draw = now;
        shared.pane.set_message(render_pane(&st.lines));
    }
}

/// Render the pane content with per-kind colors
fn render_pane(lines: &VecDeque<(Kind, String)>) -> String {
    lines
        .iter()
        .map(|(kind, text)| match kind {
            Kind::Normal => format!("  │ {text}"),
            Kind::Warning => format!("  │ {}", text.as_str().yellow()),
            Kind::Error => format!("  │ {}", text.as_str().red()),
        })
        .collect::<Vec<_>>()
        .join("\n")
}

/// Status bar style while no determinate progress is known
///
/// The target lives on the first line and the current phase/message on its own
/// line below, so narrow terminals are not overflowed.
fn spinner_style() -> ProgressStyle {
    ProgressStyle::default_bar()
        .template("> {spinner:.blue} {prefix}\n {msg}")
        .expect("valid template")
}

/// Status bar style with a determinate progress bar
///
/// Same two-line layout as [`spinner_style`], plus the bar on a third line.
fn determinate_style() -> ProgressStyle {
    ProgressStyle::default_bar()
        .template("> {spinner:.blue} {prefix}\n {msg} [{bar:24.cyan/blue}] {pos}/{len}")
        .expect("valid template")
        .progress_chars("=> ")
}

/// Whether stdout is a terminal
fn is_stdout_tty() -> bool {
    // SAFETY: isatty only inspects the file descriptor
    unsafe { libc::isatty(libc::STDOUT_FILENO) == 1 }
}

/// Default log file path for a given timestamp
fn default_log_path(timestamp: &str) -> PathBuf {
    let dir = ProjectDirs::from("com", "pkh", "pkh")
        .map(|dirs| dirs.cache_dir().join("logs"))
        .unwrap_or_else(std::env::temp_dir);
    dir.join(format!("deb-{timestamp}.log"))
}

static SIGINT_LOG_PATH: Mutex<Option<PathBuf>> = Mutex::new(None);
static SIGINT_INSTALLED: AtomicBool = AtomicBool::new(false);

/// Install a best-effort Ctrl+C handler clearing the widget and pointing at
/// the log file before exiting
fn install_sigint_hook(log_path: &Path) {
    update_sigint_log_path(log_path);
    if SIGINT_INSTALLED.swap(true, Ordering::SeqCst) {
        return;
    }

    // SAFETY: installing a signal handler; the handler itself is best-effort
    // (it performs non async-signal-safe operations, acceptable here because
    // it immediately exits afterwards).
    unsafe {
        libc::signal(libc::SIGINT, on_sigint as *const () as usize);
    }
}

/// Point the sigint handler at the current log file location
fn update_sigint_log_path(log_path: &Path) {
    *SIGINT_LOG_PATH.lock().unwrap() = Some(log_path.to_path_buf());
}

extern "C" fn on_sigint(_sig: libc::c_int) {
    // Best-effort cleanup: clear leftover widget lines and show the cursor
    let _ = execute!(
        std::io::stdout(),
        Clear(ClearType::FromCursorDown),
        cursor::Show
    );
    if let Ok(guard) = SIGINT_LOG_PATH.try_lock()
        && let Some(path) = guard.as_ref()
    {
        eprintln!("\nInterrupted — full log: {}", path.display());
    }
    // SAFETY: raw exit bypassing destructors, intended in a signal handler
    unsafe {
        libc::_exit(130);
    }
}